Various metal materials have been used for electric parts, and micronization of the electric parts is being developed every year. A typical example is a thermoelectric device. In the thermoelectric device, a voltage is generated by providing a difference in temperature between the opposite ends thereof. A device designed to extract the voltage as electric energy is a thermoelectric power generator. Such a thermoelectric device wherein heat energy can be converted directly into electric energy has attracted much attention as an effective means of utilizing heat energy, as represented by the case of waste heat utilization.
Meanwhile, the flow of a current caused to occur through the thermoelectric device results in generation of heat at one end thereof, and absorption of heat at the other end thereof. This is due to the Peltier effect, and a cooler can be manufactured by taking advantage of such a phenomenon of heat absorption. This type of cooler which does not comprise mechanical components and can be reduced in size has an application as a portable refrigerator, or a localized cooler for lasers, integrated circuits, and the like.
The thermoelectric device which is used as a thermoelectric power generator or cooler is simple in construction, and is in a more favorable condition for miniaturization as compared with other types of power generators, and there will not arise a problem of leakage or depletion of electrolyte as with the case of a redox cell. Therefore, the thermoelectric device has promising prospects for application to portable electronic devices such as an electronic wrist watch.
The thermoelectric device is formed with plural thermocouples consisting of p-type and n-type thermoelectric semiconductors, aligned in series.
In the case of the difference in temperature between a cold junction and a hot junction of the thermoelectric device is 1.3.degree. C., in order to obtain voltage of more than 1.5 V which is necessary for driving the wrist watch, more than 2000 pairs of thermocouples are required even with BiTe-based thermocouples which are said to have a high performance index.
The thermoelectric device is required to be as small in size as possible, because it is disposed in a highly-limited space such as the interior of a wrist watch. Therefore, a highly-dense and minute thermoelectric device in size is required so that many thermocouples can be arranged in a limited area.
For example, Japanese Patent Laid-open No. 63-20880 discloses a method of fabrication of a miniaturized thermoelectric device with a plurality of thermocouples in high density.
In this publication, mentioned is a method of fabrication to form a p-type bar-shaped device and an n-type bar-shaped device in a manner such that the p-type and n-type thermoelectric materials in a thin sheet-like shape are laminated on top of each other in layers while interposing a heat insulating material between respective p-type and n-type thermoelectric material layers, and grooves are formed at fixed intervals in a perpendicular direction to a laminated surface. The p-type bar-shaped device and the n-type bar-shaped device are connected in series with electrode materials at each end.
The thermoelectric device formed with the above-described method has a size of 30.times.20.times.3.5 (mm), containing 3500 pairs of thermocouples, which amounts to 7000 pieces of the total of the bar-shaped devices in an extremely high density.
However, in the case of connecting another circuit to this thermoelectric device, current must be taken out from one of the electric patterns shown here. When ordinary solder is used to take out the lead line for this purpose, it needs very fine work and a special device. In addition, formation of a large electrode for the lead line requires a large thermoelectric device itself, which is inconvenient to dispose in a limited space.
It is an object of the present invention to solve the above-described disadvantages and to provide a structure of the thermoelectric device which takes out a lead line easily and efficiently while having a fine and high-density structure, and a method of fabrication thereof.